A first conventional magnetic head includes a ceramic substrate and a soft magnetic layer formed on the ceramic substrate. In such a magnetic head, the soft magnetic layer is made of FeSiAl or FeMN (M=Ti, Zr, Nb, Mo, Hf or Ta) having a large saturation magnetization. The ceramic substrate includes a great amount of oxide such as NiO, MnO, CoO, etc. each having a large thermal expansion factor close to that of the soft magnetic layer. In fabrication, FeSiAl or FeMN is grown on a surface of the ceramic substrate by gas phase crystal growth such as sputtering and is heated by more than 500.degree. C., so that the soft magnetic layer is formed.
According to the first conventional magnetic head, however, there are disadvantages in that oxygen in the ceramic substrate is diffused to the soft magnetic layer when the thermal treatment is carried out, because a formative energy of oxide in the soft magnetic layer is lower than that of the ceramic substrate. As the result, magnetic property of the soft magnetic layer is reduced. This disadvantage is noteworthy when a ceramic substrate includes NiO and CoO. In addition, it is difficult that the surface of the ceramic substrate is flattened, because a ceramic is difficult to be ground. Therefore, the ceramic substrate and the soft magnetic layer are not fastened closely.
A second conventional magnetic head includes a ceramic substrate, a soft magnetic layer, and a bonding glass layer formed between the soft magnetic layer and the other ceramic substrate.
According to the second conventional magnetic head, however, there is a disadvantage in that a yield of the magnetic head is not high, because the bonding glass layer is difficult to provided a sufficient bonding strength on the soft magnetic layer.